The present invention relates generally to transceiver circuits and in particular the present invention relates to transceiver circuits that can operate in harsh wiring networks.
A data network is a system that permits individual devices to exchange data with one or more other devices. Data network systems encompass computer networks including a number of computers, printers, or other peripheral equipment linked together. Data networks also include communication with automated control and monitoring equipment, telemetry devices, alarm devices, or the like. Historically the devices of a network have been linked together by dedicated wiring. Dedicated wiring, however, has a number of recognized limitations and drawbacks, including the high cost, delay, inconvenience and in some circumstances complexities of installation in existing buildings, and once installed, the cost and inconvenience of expanding or reconfiguring the system. Alternative approaches have emerged using wireless radio-frequency, infrared transmissions or using the AC power lines as the network communications medium.
In power line data communications the transmitted data is piggybacked onto an existing power line in addition to the electrical AC line current already present for delivering electrical power. Using the power line as the medium for communications is particularly convenient because a power line will always be present to provide power to the various nodes of the network, and this avoids the need to retrofit the work area with dedicated wiring. The power line, however, presents an extremely hostile electrical environment. The transmission of data over interconnecting wires suffers from several noise and attenuation phenomena. Specifically, when an AC power line is used as the transmission medium, this type of system generally exhibits unpredictable transmission characteristics such as extreme attenuation at certain frequencies, phase changes along the transmission route, and notches and discontinuities. The power line characteristics may vary significantly as load conditions on the line vary, e.g., a variety of other loads being added or removed from the current-carrying line. Such loads include industrial machines, the various electrical motors of numerous appliances, light dimmer circuits, heaters and battery chargers. To provide communication on such noisy lines, transceiver circuits can be provided which include complicated synchronization and timing recovery circuitry.
Data communication speeds over power lines are currently limited to approximately 100 to 400 Kbps. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a high-speed data transmitter and receiver for communicating over household type power lines and telephone circuits.
In one embodiment, a receiver circuit comprises an external coupling circuit for receiving an analog input signal, an amplifier circuit for amplifying the analog input signal, and an analog filter having an input connection to receive the analog input signal which comprises a data signal and noise signals. The analog filter removes some out-of-band noise from the analog input signal and provides an analog output signal. The receiver circuit further comprises an analog to digital circuit coupled to an output connection of the analog filter to convert the analog output signal to a digital signal, and a signal detector coupled to the analog to digital circuit. The signal detector detects an arrive time of the data signal, and normalizes an output signal from the signal detector based upon a detected maximum amplitude. An equalizer circuit is provided which comprises a recursive filter using variable weight functions which are controlled by a calculated error signal.
In another embodiment, a transceiver circuit comprises a receiver circuit and a transmitter circuit. The receiver circuit comprises an analog filter having an input connection to receive an analog input signal which comprises a data signal and noise signals, an analog to digital circuit coupled to an output connection of the analog filter to convert the analog output signal to a digital signal, a signal detector coupled to the analog to digital circuit, and an equalizer circuit comprising a recursive filter using variable weight functions which are controlled by a calculated error signal. The transmitter circuit comprises a pulse generator circuit, and a spectral shaping filter.